In order to achieve industries enabling sustained growth, there is a social demand for a new energy generation and distribution system that satisfies both higher efficiency in energy consumption and reduction of industrial waste. Aimed at such energy generation and distribution, new energy-communication integrated networks are being built around the world.
The energy-communication integrated network is intended to connect various devices involved in generation, distribution, and consumption of energy over the network to share information on the operation status of the devices and surrounding environments among all or specific ones of the devices, and control the operation status of the devices connected over the network using the information to optimize the performance of all the network-connected devices on the whole.
The devices to be connected for establishment of the network are very large in number. Therefore, the use of a wireless network is expected to reduce the introduction cost and maintenance cost of the network.
The wireless network can be expected to decrease its introduction and maintenance costs, but data flowing on the network is subjected to external noise and disturbance waves due to the physical properties of electromagnetic waves as a transmission medium of wireless communication. It is thus difficult to ensure reliability of control and monitoring information on the various devices using the data.
In particular, when the various devices connected over the energy-communication integrated network generate and distribute resources directly linked to ordinary citizens' life such as electric power, water, and gas, the degradation and loss of the data would inevitably cause heavy damage to civilian life. The problem of difficulty in ensuring reliability of control and monitoring information on the various devices is definitely to be solved to implement the energy-communication integrated network by wireless technology.
In wireless communications, the various devices existing between the communication transmission and reception points act as electromagnetic wave scatterers. Therefore, communications are carried out through a plurality of different paths from the transmission point to the reception point via a plurality of multiple reflection propagation paths caused by reflection from the various devices. The plurality of paths caused by multiple reflection is specific to the transmission and reception points. A signal from the transmission point reaches any spatial point other than the transmission and reception points through a path different from the plurality of paths from the transmission point to the reception point, and a signal generated from the other spatial point reaches the reception point through a path different from the plurality of paths from the transmission point to the reception point.
Therefore, selecting or combining the plurality of paths from the transmission point to the reception point may allow transmission of information that could not be acquired at other spatial points between the transmission and reception points. PTL 1 describes a background technique based on such a principle. According to the technique in PTL 1, an information signal to be transmitted is digitized, a balanced modulator and two orthogonal antennas are used for a transmitter, and data is transmitted with two polarization states of rotation/fixation in correspondence with the digital signal. In addition, PTL 2 describes that two lines of data are generated based on an information signal to be transmitted, and are transmitted by rotational polarization in different rotating directions.